1. Field of the Invention
The present invention relates to methods and systems for generating electrical energy in a downhole environment and, more particularly, to methods and systems utilizing a flow of drilling fluid to generate electricity downhole.
2. Background and Related Art
The goal of accessing data from a drill string has been expressed for more than half a century. As exploration and drilling technology has improved, this goal has become more important in the industry for successful oil, gas, and geothermal well exploration and production. For example, to take advantage of the several advances in the design of various tools and techniques for oil and gas exploration, it would be beneficial to have real time data such as temperature, pressure, inclination, salinity, etc. Several attempts have been made to devise a successful system for accessing such drill string data. However, due to the complexity, expense, and unreliability of such systems, many attempts to create such a system have failed to achieve significant commercial acceptance.
In U.S. Pat. No. 6,670,880 issued to Hall et al. (“Hall”), the inventors disclosed a “downhole transmission system” that overcomes many of the problems and limitations of the prior art. In the Hall system, data is transmitted in real time along the drill string by way of network hardware integrated directly into the drill string. This network hardware enables high-speed communication between various tools and sensors located along the drill string with surface analysis, diagnostic, and control equipment.
Hall thus solves many of the problems of the prior art by providing a reliable high-speed connection between downhole drilling components and the surface. Novel apparatus and methods are needed, however, to ensure an efficient and reliable energy source to power such a network.
Traditionally, oil and gas industries have relied on wireline conductors or batteries to supply electricity to particular downhole tools and sensors. Wireline conductors, however, cannot be used while drilling and are often unreliable since significant energy loss can be caused by the resistance or impedance of a long wireline conductor. In addition, extreme conditions downhole may corrode wireline conductors, necessitating frequent conductor repair and/or replacement.
Batteries, too, fail to adequately ensure an efficient and reliable energy source over time as they have an inherently finite life, requiring frequent replacement and/or recharging. This factor is particularly problematic in a downhole application where batteries tend to be inaccessible absent considerable effort in disassembling at least a portion of the drill string. Battery function also tends to be impaired as a result of extreme temperatures and pressures downhole, resulting in reduced electrical energy production and sub-optimal tool and/or sensor performance.
Although downhole electrical generators have been attempted to overcome some of the foregoing problems, known generators create additional problems that limit their usefulness in the downhole drilling industry. Specifically, some known generators obstruct the central borehole of the drill string, thus inhibiting a continuous flow of drilling fluid and precluding presentation of a wireline tool or other equipment downhole. Moreover, many known generators are designed for implementation in production wells rather than in connection with downhole drilling strings. Many known generators are also considerably complex devices of substantial mass, and are thus costly to implement and maintain, and difficult to replace and/or repair. Finally, many known generators are ill-equipped to weather extreme temperatures, pressures and corrosive conditions downhole.
Accordingly, what is needed is an improved downhole electrical generator device that may be implemented in connection with a downhole drill string in a position that does not obstruct a central borehole thereof. What is also needed is an improved downhole electrical generator device that is simple and inexpensive to manufacture, implement, and maintain. What is also needed is an improved downhole electrical generator having relatively small dimensions capable of easy access and repair. Finally what is needed is an improved downhole electrical generator device that is able to withstand extreme temperatures, pressures and corrosive conditions downhole.
Such methods and systems are disclosed and claimed herein.